CORRELATED REFLECTION AND CONDUCTIVITY MEASUREMENTS ON (2,5-DIMETHYL-DICYANOQUINONEDIIMINE)(2)CU CRYSTALS AND FILMS

We present correlated temperature dependent reflection and conductivit y measurements on crystals and films of the undeuterated (h(g)) and th e partly deuterated (d(6)) (2,5-dimethyldicyanoquinonediimine)(2)Cu ra dical anion salt. Using thin optical fibers, it was possible to study individual needle like crystals of a diameter of only a few mu m. The temperature dependence of the reflectivity of single (d(6)) needles in the visible and the near-infrared region shows a ''dip'', which coinc ides with the phase transition in the conductivity. To interpret our d ata, we extended the commonly used models for the conductivity from Dr ude and Epstein, so that we are able to deal with reflection and condu ctivity in terms of one consistent model. For the (d(6)) films, a meta l-insulator phase transition has been proved by reflection and conduct ivity. With the assumption of a broad distribution of different phase transition temperatures for the crystallites of the films, the observe d spectra of films can also be treated with the model used for the cry stals. (C) 1995 American Institute of Physics.